Lithium ion batteries, nickel-hydrogen batteries, and other secondary batteries have recently gained importance as power sources for installation on vehicles and also as power sources for personal computers and portable terminals. In particular, lithium ion batteries, which have small weight and make it possible to obtain a high energy density, are expected to be advantageously used as high-power electric power sources for installation on vehicles. The batteries of this type are known to have a structure provided with a wound electrode body obtained by laminating a sheet-like positive electrode and a sheet-like negative electrode together with a separator and winding the laminate.
However, in the batteries of this type, the electrode body and an exterior case have to be manufactured separately and the electrode body has to be thereafter accommodated in the exterior case. A metallic package is often used as the exterior case. In this case, the electrode body has to be packaged with an insulation film in order to insulate the metal package and the electrode body from each other. For example, Patent Document 1 discloses an angular sealed battery configured by covering three surfaces, namely, two side surfaces and a lower surface of an electrode assembly coupled body obtained by connecting a plurality of electrode assemblies (a laminated electrode body obtained by laminating alternately a large number of positive electrode sheets and a large number of negative electrode sheets, with a separator being interposed therebetween) with a sheet of a U-like cross-sectional shape (a single layer of polypropylene or polyethylene or a multilayer laminated structure thereof) and inserting and disposing the electrode assembly coupled body together with the sheet of a U-like cross-sectional shape inside an accommodation space of an angular battery case. Patent Document 2 is another document illustrating prior art.    Patent Document 1: Japanese Patent Application Laid-open No. 2003-51335    Patent Document 2: Japanese Patent Application Laid-open No. 2006-120419